The invention relates to a method and system (machine) that makes water at the location of water usage. This need is spurred by the fact that providing water to remote locations is often difficult. Further, with sea levels rising and land becoming scarce, setting up water transportation infrastructure such as roads for water carrying tankers or transportation pipelines is an added burden in terms of land usage. Transportation of water with tankers and other means uses fuel, which is not a sustainable method of development and growth. For example, soldiers going to war or hikers and campers traveling to remote locations need to carry essential commodities among which is bottles of water. This load can be reduced if they could carry their own water generation device.
Numerous techniques have been developed to obtain potable water. Among the mechanical techniques, the most common is to condense moisture in the air using a refrigerant based cooling coil and collecting the condensed water in a water tank. This technique is intrinsically inefficient due to the limitations of the refrigeration cycle. Details of this technique and examples can be found in U.S. Pat. Nos. 6,755,037, 3,740,959, 4,433,552 and 6,588,225. Another technique removes water from air by compressing the air to such a high extent that water vapor condenses to form liquid water. However this technique is not economically feasible due to high costs and also, not preferable due to moving parts. Details of this technique can be found in U.S. Pat. Nos. 6,453,684 and 6,230,503. The mechanical water generation systems listed above all suffer from reduced efficiency at lower relative humidity. When the relative humidity becomes low, i.e. in the sub 30% range, mechanical water generation systems become very energy inefficient and are not economically feasible. Ironically, low humidity conditions are where there is the greatest need for water generation both portable and otherwise.
To address the inherent inefficiencies of mechanical systems at low humidity, chemical-mechanical systems have been developed which combine chemical means of water extraction with mechanical water condensation. The chemical system in some of these devices is made up of liquid desiccants such as in U.S. Pat. No. 6,156,102. However, liquid desiccant systems have to be constantly refilled and the process of regaining water from water-desiccant mixture through distillation systems suffers from high energy requirements and inability to strip all of the liquid desiccant from recovered water hence leading to chemically contaminated and not pure water. Other desiccant systems have used solid desiccants such as silica gel and molecular sieves. These systems are intrinsically batch processes and hence can be used for limited time. Some prior inventions using solid desiccants can be found in U.S. Pat. Nos. 4,344,778, 4,342,569, 4,313,312, 4,146,372 and 4,219,341. To address this issue of continuous functioning, systems which make use of alternate adsorption desorption beds such as has been mentioned in U.S. Pat. No. 4,304,577 have been designed. However, there has been no focus to optimize the water production quantity and efficiency.
Another design with solid desiccants is the rotating wheel system. This allows for continuous water production and has been commonly used in dehumidifiers. However, the desorbed water is left in the waste streams (impure water) and the water production rate is always lower than in packed bed systems. Implementation of rotating wheel systems can be found in U.S. Pat. Nos. 6,099,623, 5,931,015, 5,526,651, 3,844,737, 5,709,736 and 5,170,633.
A cost effective system to generate pure water which can then be made potable is needed to address these problems. Further the ability to operate in low humidity environments is an added benefit.